lockdep: Take read/write status in consideration when generate chainkey
Currently, the chainkey of a lock chain is a hash sum of the class_idx
of all the held locks, the read/write status are not taken in to
consideration while generating the chainkey. This could result into a
problem, if we have:
P1()
{
read_lock(B);
lock(A);
}
P2()
{
lock(A);
read_lock(B);
}
P3()
{
lock(A);
write_lock(B);
}
, and P1(), P2(), P3() run one by one, when running P2(), it's detected
such a lock chain A -> B is not a deadlock, then it's added in the chain
cache, and then when running P3(), even if it's a deadlock, we could
miss it because of the hit of chain cache. This could be confirmed by
self testcase "chain cached mixed R-L/L-W ".
To resolve this, we use "hlock_id" to generate the chainkey, the
hlock_id is a tuple (hlock->class_idx, hlock->read), which fits in a u16
type. With this, the chainkeys are different is the lock sequences have
the same locks but different read/write status.
Besides, since we use "hlock_id" to generate chainkeys, the chain_hlocks
now store the "hlock_id"s rather than lock_class indexes.
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
1 file changed
